Functional redundancy and divergence of β-carbonic anhydrases in Physcomitrella patens

Main conclusion beta -carbonic anhydrases, which function in regulating plant growth, C/N status, and stomata number, showed functional redundancy and divergence in Physcomitrella patens.AbstractCarbonic anhydrases (CAs) catalyze the interconversion of CO2 and HCO3-. Plants have three evolutionarily unrelated CA families: alpha-, beta-, and gamma -CAs. beta CAs are abundant in plants and are involved in CO2 assimilation, stress responses, and stomata formation. Recent studies of beta CAs have mainly examined C-3 or C-4 plants, whereas their functions in non-vascular plants are mostly unknown. In this study, phylogenetic analysis revealed that the evolution of beta CAs were conserved between subaerial green algae and bryophytes after terrestrialization event, and beta CAs from some cyanobacteria might begin evolving for the adaptation of terrestrial environment/habitat. In addition, we investigated the physiological roles of beta CAs in the basal land plant Physcomitrella patens. High Pp beta CA expression levels in different tissues suggest that Pp beta CAs play important roles in development in P. patens. Plants treated with 1-10 mM NaHCO3 had higher fresh and dry weight, Pp beta CA expression, total CA activity, and photosynthetic yield (Fv/Fm) compared with water-treated plants. However, treatment with 10 mM NaHCO3 influenced the C/N status. Further study of six Pp beta ca single-gene mutants revealed that Pp beta CAs have functional redundancy and divergence in regulating the C/N ratio of plants and stomatal formation. This study provides new insight into the physiological roles of beta CAs in basal land plants.